Radiation Modification of Natural Polymers

Lecturer : Assoc. Prof. Dr. Murat Şen

Hacettepe University Department of Chemistry,Polymer Chemistry Division, 06532, Beytepe, Ankara, TURKIYE

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Topic: Radiation Modification of Natural Polymers

Major Processes For the Radiation Modification of Natural Polymers

Cross-linkingNatural rubber latex

Crosslinking of polysaccharides

Degradation

Cellulose fibers obtained from wood pulpDegradation of polysaccharides

Preparation of blends

Preparation of synthetic-natural polymer blends

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Various research works have been performed on radiation vulcanization of natural rubber latex (RVNRL) since it possesses several advantages over sulfur vulcanization such as

Topic: Radiation Modification of Natural Polymers [1]

Polyfunctional monomers which contain more than two polymerizable C C double bonds in a molecule, and monofunctional acrylic monomers were used as vulcanization accelerators. Among the monofunctional monomers,n-butyl acrylate (n-BA) is the most effective vulcanization accelerator because it not only imparts much better physical properties at lower Dv but also unreactedn-BA is not retained in the final product

The low glass transition temperature of poly(n-BA) and a high probability of chain transfer reaction of n-BA during polymerization are closely related to its high sensitizing effect

the absence of nitrosoamines compounds

better transparency

very low cytotoxicity

and less rubber proteins that causes allergic response

Radiation vulcanization of natural rubber latex

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Many attempts were made to investigate an alternative accelerator to be used in radiation vulcanization of natural rubber latex (RVNRL)

Trimethylol propane tri-methacrylate (TMPTMA)Phenoxy polyethylene glycol acrylate(polyfunctional monomer) (PPEGA)Phenoxy ethyl acrylate (PEA),

Topic: Radiation Modification of Natural Polymers [2]

Variation of tensile strength of NR vs dose

Variation of tensile strength of RVNRL prepared using TMPTMA at various doses of radiation.

Gelation dose

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Topic: Radiation Modification of Natural Polymers [17]

Rayon is produced from viscose, a polymer made from cellulosic materials such as wood pulp

Cellulose fibers extracted from wood pulp can be converted to a thick liquid called viscose, which is used

to make commercial products such as rayon fabrics and cellophane films.

The molecular weight of the natural cellulose is reduced by treatment with sodium hydroxide and heat. Then this material is dissolved in carbon disulfide to make viscose

Initial irradiation of the cellulose causes a reduction in molecular weight, and enables the rest of the process

to be completed in less time with less chemical treatment

This reduces the cost and also reduces the environmental pollution. The dose requirement is about

15 kGy

VISCOSE - RAYON AND CELLOPHANE

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Topic: Radiation Modification of Natural Polymers [16]6

Topic: Radiation Modification of Natural Polymers

ALGINATES

Food stabilizer, gelling agent, encapsulation

matrix, plant growth stimulator

CARRAGEENANS

Food processing, thickening agent, film forming,

agriculture, horticulture, anti-HIV activities

CHITOSAN

Food processing, paper and textile industries,

photographic processing, biomedical applications

due to antifungal, antibacterial, antitumor activities

as well as immuno-enhancing effects and protective

effects against infection

POLYSACCHARIDES

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OO

O

K

O3SO

OHO

CH2

OHO

OHOH2C

OO

OHO

OCH2 K O

OHO

CH2OHO3SO

Possible gelation mechanism of -carrageenan in aqueous solution: (----),

ionic bonding; ( ), electrostatic forces of attraction.

Topic: Radiation Modification of Natural Polymers 8

• Gigartina (France, Argentina/Chili, Morocco) • Chondrus (France, North Atlantic) • Iridaea (Chili) • Eucheuma (Philippines/Indonesia)

Topic: Radiation Modification of Natural Polymers 9

• Natural polysaccharides from seaweeds (brown algae)

• Alginate is phycocolliod

• Consists of linear chains composed of two monosaccharides;

– D-mannuronic acid (mannuronate) (M)

– L-guluronic acid (guluronate) (G)

Topic: Radiation Modification of Natural Polymers

O

O

OH

COONa

HO O

OH

HO

COONa

O

O

OH

O

-OOC

OH

O

OH

COONa

OH

OO

O

-OOC

HO O

HO

COO-OH

OH

O

O

OH

O

-OOC

OH

Sodium Alginate

D-guluronate (G)

D-mannuronate (M)

O

COONa

O

OH

HO O

OH

COONa

HO

G G M M G

Sodium Alginate

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• Water-soluble gums sulfated polysaccharides

• 1,3 linked β-D- galactose and

1,4 linked α-D- galactose units.

• Anionic poly-electrolytes.

• Three main branches.

– Kappa

– Iota

– Lambda

Topic: Radiation Modification of Natural Polymers

Carrageenans

O

OH

CH2OH-O3SO

O OO

OH

H2C

O

OCH2OSO3

-

-O3SO

O

-O3SO

CH2OHOH

O O

O

OSO3-

H2C

OO

O

OH

CH2OH-O3SO

O

ι-carrageenan

λ-carrageenan

κ-carrageenan

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Topic: Radiation Modification of Natural Polymers

The most essential medical applications of chitosan are as follows - wound healing promoting dressings- dermatological agents- biodegradable carriers for slow release drugs- anticoagulant agents- optimological, dentistical and orthopedic agents- tumor cell metabolism reducing agents

Chitosan

It occurs in the shells of crabs, shrimps, prawns, lobsters, insects as well as some fungi wall cells.

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Topic: Radiation Modification of Natural Polymers

DEGRADATION OF POLYSACCHARIDES

• Chemical

• Microwave

• Enzymatic

• Photolysis

• Ultrasound

• Radiation

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• Radiation cause the breakage of glycosidic bonds

• Molecular weight, viscosity,gel strength decreases

• Alginates were irradiated as solid state or in aqueous solutions

RADIATION-INDUCED DEGRADATION OF ALGINATE

Topic: Radiation Modification of Natural Polymers 14

Alginate degradation under N2 and O2 conditions

Topic: Radiation Modification of Natural Polymers [3] 15

Color Change of Irradiated Alginate

Topic: Radiation Modification of Natural Polymers [3] 16

UV Spectra of Alginate Irradiated with Various Doses

Topic: Radiation Modification of Natural Polymers [3] 17

Appearance of mango treated with irradiated chitosan after 12 and 17 days storage

Fresh mangoes were dipped into the irradiated chitosan solution (1%) and dried for surface coating.

Topic: Radiation Modification of Natural Polymers [8]

Mango treated with irradiated chitosan

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Rice was cultivated for 9 days in hydroponic solution with 20

ppm alginate irradiated in 4% solution

Alginate was irradiated at 100 kGy in 4% solution and rice

was cultivated for 9 days

Effect of irradiated alginate on rice growth

Effect of concentration of degraded alginate

on rice growth

(1) Without alginate(2) (2) 20 ppm alginate irradiated (3) at100 kGy in 4% solution(3) 20 ppm alginate irradiated At 500kGy in solid state.

Growth of rice with alginate irradiated in liquid and dry

Topic: Radiation Modification of Natural Polymers [9] 19

Topic: Radiation Modification of Natural Polymers [9]

Effect of concentration of degraded alginate on peanut growth. Alginate was

irradiated at 100 kGy in 4% solutionand peanut was sprayed with alginate

solution for 15 days after 30 days cultivation

Change in net photosynthesis of peanut plant by foliar spraying of irradiated

alginate. : without alginate,

:sprayed with irradiated alginate.

Effect of degraded alginate on peanut growth

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Rice was cultivated for 9 days in hydroponic solution with 100 mg/ml chitosan.

From left, (1); control (without chitosan), (2); with unirradiated chitosan,

(3)–(5); 20, 50 and 100 kGy-irradiated chitosan

Change in rice growth with treatment of irradiated

chitosan.

Topic: Radiation Modification of Natural Polymers [10]

Rice was cultivated for 9 days in hydroponic solution with

100 mg/ml chitosan

shoot; root; shoot without chitosan root without chitosan.

Effect of irradiated chitosan for rice growth

Effect of radiation-degraded chitosan on plants stressed with vanadium

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Rice and soybean plants were damaged at 2.5 mg/ml V (in VCl3).

These damages were reduced by application of radiation-degraded chitosan.

Bioimaging analyzer system (BAS) images of 48V in rice under V stress (10 mg/ml) with 50 mg/ml of irradiated chitosan.

Left: with chitosan

right: without chitosan.

Topic: Radiation Modification of Natural Polymers [10] 22

Topic: Radiation Modification of Natural Polymers

New topics

A composite material for dietary applications

Microgel particles (swelling)

Radiation-modified chitosan (effective lipid+cholesterol binding)

Lipid+cholesterol binding

Synthetic biocompatible polymer Microgels

Matrix Fat-bindingagent

Action

Crosslinking

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New topics

Binding of lipids: ca. 20 g per 1 g of our composite substrate

Lipid + cholesterol binding

O

OH

NH3

HO O

nClO4

Preliminary animal studies under way (with positive results).

Fat binding

Topic: Radiation Modification of Natural Polymers 24

Polysaccharides undergo degradation by irradiation

Irradiation of polysaccharides at paste-like condition will led to crosslinking and form hydrogel.

Topic: Radiation Modification of Natural Polymers [11-12] 25

crosslinked CMC mat in the surgical

operation room

CMC gel

plastic bag containing CMC gel,

Topic: Radiation Modification of Natural Polymers [13]

Crosslinked CMC is suitable for healthcare product such as surgical operation mats for prevention of bedsores

High viscous solution of 20% CMC was pressed into a plastic bag and irradiated with 10 kGy

commercialized as‘‘Non-bedsore’’ in Japan.

Such mats were tested by 68 patients in a hospital. No bedsores were observed in 64 patients andonly red spots appeared on 4 patients immediately aftersurgical operation

This result reveals that the crosslinkedCMC mat is extremely effective to prevent bedsores during surgical operation

This CMC gel mat is considered to disperse the body pressure and tomaintain the best circulation of blood during operation

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Topic: Radiation Modification of Natural Polymers [14-16]

Preparation of synthetic-natural polymer blends

PVP-kappa carrageenan

PVP-agar

PVA-agar

Chitosan-grafted N-isopropylacrylamide

Chitosan/pHEMA membranes

Synthesis of antibacterial PVA/CM-chitosan blend hydrogels

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